The present invention relates to a lithographic newspaper printing press for printing four pages across the first and the second side of a running web at every revolution.
Lithographic newspaper printing presses for printing four single or multiple colored newspaper pages across the first and the second side of a running web (16-page presses) are generally known in the art and are used for printing single or multicolored daily or free newspapers.
From the applicant""s Galaxy-series presses, it is known to employ blanket-to-blanket printing units having plate cylinders, each carrying two printing plates around and four printing plates across (8xc3x972-design), whereby each printing plate carries the image of a corresponding newspaper page to be printed.
Owing to the double-size blanket cylinders and the corresponding double-size plate cylinders carrying two printing plates around the circumference of each cylinder, such 8xc3x972-design presses usually comprise a high weight and are comparatively large in size and, therefore, require an expensive reinforced bottom plate or foundation for supporting the printing units and an enlarged pressroom space.
Furthermore, the paging flexibility of 8xc3x972-design presses is generally comparatively low, and the page-breakxe2x80x94the number of pages that have to be printed without producing a blank page in the printed productxe2x80x94of such presses usually amounts to four pages.
U.S. Pat. No. 3,335,663 purports to disclose a plate lock-up mechanism mounted to a single-size plate cylinder, on which altogether four conventional printing plates are mounted across the width of the cylinder. Although in the document it is mentioned, that the disclosed cylinder is a reversible cylinder which can be used in a newspaper printing press, it does neither describe nor show any details about a printing press.
U.S. Pat. No. 3,230,879 describes a plate lock-up mechanism for a double-size plate cylinder carrying four stereotype printing plates across and two of those plates around the circumference. The document gives no information about the kind of printing presses the cylinder can be used for.
Having outlined the state of the art and its attendant disadvantages, it is an object of the present invention to provide a high-performance 8-page newspaper printing press for printing four newspaper pages across, which is small in size, light in weight and easily accessible, which can be operated with a small number of staff and which allows an easy and quick change of printing plates and printing blankets.
It is another object of the present invention, to provide a newspaper printing press in which the width of the unprinted margin of each printed newspaper page is reduced to only a fraction of the width of the minimum margin achievable with conventional prior art newspaper presses.
According to exemplary embodiments of the present invention, a lithographic newspaper printing press comprises a printing unit with a housing having a first side wall and a second side wall, a first and a second plate cylinder, each being rotatably mounted in said housing, said plate cylinders having a length being substantially four times the width of a newspaper page and having a circumference being substantially equal to the height of a newspaper page; a first and a second blanket cylinder associated with said first and second plate cylinders, each of said first and second blanket cylinders having substantial diameter as the associated plate cylinder, an axially removable continuous blanket sleeve mounted on each of said first and second blanket cylinders, whereby each of said first and second blanket cylinders are cantilevered in said first side wall of said housing, when said continuous blanket sleeves are removed from said first and second blanket cylinders.
According to a further embodiment of the present invention, the first and second plate cylinders and the associated blanket cylinders of each printing unit are arranged substantially in line.
Pursuant to another embodiment of the invention, each couple formed of a plate cylinder and its associated blanket cylinder in a printing unit is driven by a separate motor.
According to a preferred embodiment of the invention, each of the first and second plate cylinders is carrying four conventional flat printing plates which are wrapped around and held on the plate cylinders by a plate lock-up mechanism, whereby the printing plates are arranged on the plate cylinder side by side.
In an alternative embodiment, each of the first and second plate cylinders can carry four axially removable continuous printing plates, whereby the first and second plate cylinders are cantilevered in one sidewall of said housing, when the continuous printing plates are axially removed from the plate cylinder through a respective aperture formed in the other side wall of the housing. In this embodiment of the present invention, the continuous axially removable printing plates are preferably arranged on the respective plate cylinder side by side.
Alternatively, the conventional flat plates or the axially removable continuous plates can be arranged on the associated plate cylinder in predetermined distances from each other.
According to the preferred embodiment of the invention, the length of said first and second plate cylinders is in the range be en 1200 mm and 1700 mm, and the circumference of each of said first and second plate cylinders is in the range between 470 mm and 650 mm. The length to diameter ratio of said first and second plate cylinders is preferably in the range between 8.4:1 and 9:1.
According to an exemplary embodiment of the invention, four printing units, each printing unit printing a different color, are preferably arranged on top of each other, whereby the web is running substantially vertically from one unit to the other. Additionally, there can be a fifth printing unit arranged on top of the four printing units. In this embodiment, the four printing units are preferably for printing the colors yellow, magenta, cyan and black, and said fifth printing unit is used as an imprinting unit for printing spot-colors which are different from said colors of said four printing units.
Alternatively, the fifth printing unit is printing the same color as one of said four printing units and is operated in alternation with said printing unit printing the same color, so that the respective printing unit currently not in operation can be equipped with new blankets or with printing plates for the next print job, while the other printing units are in operation.
The printing press according to the present invention is eventually preferably used, together with a known pinless folding apparatus for processing the printed web into signatures, in order to minimize the margin of each signature and therewith the amount of paper needed for a specific print job.
The printing press according to the present invention has a number of advantages which will be described herein below.
Firstly, owing to the small diameter of the plate cylinder, the number of printing plates needed for each print job is only half the number needed for known 16-page-presses carrying two identical printing plates around the circumference and four printing plates across the width of the web. Thus, the costs and space needed for producing and storing the printing plates tremendously reduced. Furthermore, in a newspaper printing press according to the present invention, the number of page-breaks or page-jumps is reduced to two, so that the flexibility of paging is increased, as compared to 8-presses in which the number of page-breaks usually amounts to four. Accordingly, with a newspaper printing press according to the present invention, there is a much higher flexibility in arranging the set-up of each newspaper page, leading to a reduction of time and costs involved in pre-press. Besides, the amount of spoilage produced when a printing plate is wrongly mounted on the plate cylinder is also reduced, as compared to conventional 4xc3x972-newspaper presses.
Secondly, the downtime of the press caused by the printed web wrapping around the blanket cylinder in case of a web break or a broken blanket is significantly reduced, since the continuous printing blanket with the web wrapped around can easily be axially removed through an aperture in the side wall and be replaced by a new blanket. Thus, there is no downtime needed for removing the compressed and hardened layer of web and ink from the blanket cylinder, as it is usually needed when using conventional printing blankets.
Furthermore, owing to the low height of the printing units and the tower arrangements comprised of four or five printing units disposed on top of each other, the so-called xe2x80x9cfan outxe2x80x9d of the web is comparatively small. Accordingly, the quality of the printed products is significantly improved. Besides, the reduced height of such tower arrangements requires only one gallery for a five-unit tower arrangement, leading to an increase of working economy and a reduction of material costs. For example, the make-ready operations for setting up the fifth printing unit of a five-unit tower arrangement, when running said fifth unit in alternation with one of the other four units of said tower arrangement, can easily be performed by one person standing on said gallery, without using a ladder or any other kind of objects to stand on. Thus, the operation of a press according to the present invention having a five-unit tower arrangement does not require additional safety precautions for preventing a pressman from falling down when setting up the upper printing unit.